It is a standard procedure to prepare tissue samples for microscopic examination by embedding the tissue in paraffin and slicing the paraffin-embedded tissue very thinly with a microtome. Preparatory to embedding, the tissue is pretreated in various solutions appropriate to its examination. Typically, prior to paraffin embedding, the tissue sample is fixed, dehydrated, cleared, infiltrated with molten paraffin and, depending on the test, stained.
A histology laboratory daily receives a large number of tissue samples for examination, and it is important that the tissues be prepared as efficiently as possible. Described in my U.S. Pat. No. 3,674,396 are capsules in which a tissue sample is both prepared for embedding through exposure to various solutions and then embedded within a capsule. In these capsules, perforated walls are used to retain the tissues while accessing to the tissue the various solutions and, finally, molten paraffin. The perforations are of a minimal size; any substantial reduction in perforation size would reduce the efficiency of tissue processing and would be inappropriate for molding by current technology.
Typically, the tissue sample for examination is a unitary, connected portion of tissue; however, small parts of the tissue sample may be dislocated during tissue processing. Alternatively, the biopsy may be performed on minute fragments less than about 0.1 mm. in diameter, such as bronchial washings, cytology preparations and aspiration biopsies which may be gathered by the new skinny needles. If several tissue capsules are processed together, the processing solutions may carry these broken-away tissue particles or "floaters" from one sample to another. The transfer of even very minute particles of tissue from one sample to another may result in misleading diagnoses, particularly where the object of the examinations is to detect invasion of tissue by foreign cells, e.g., to determine whether a tumor has metastased.
It is a primary object of the present invention to provide apparatus for processing and embedding tissue samples at maximum efficiency and without cross-contamination from one sample to another. Other objects of the invention include providing continuous flow systems for tissue-processing liquids which recycle the various reagents that are used for processing the tissue, and in the economical use of processing capsule components in the end stage of tissue embedding and slicing.